The disclosure relates generally to combustor systems, and more particularly, to a control system for addressing can-to-can variation in a combustor system and a related method.
Combustor systems for such industrial devices as gas turbines often include a number of can combustors in which combustion fluids such as air, fuel and diluents are mixed and combusted. More specifically, each can combustor may include a number of burner tubes into which one or more fuels and perhaps diluents are introduced via nozzles into an air flow and combusted. After initial combustion in the burner tubes, the combustion flow enters a combustion chamber. The plurality of burner tubes may be positioned by an end cap at one end of the combustion chamber. Upon exiting a can combustor, the combustion flow mixes with that of other can combustors. Once mixed, the combined combustion flow can be directed from the combustion chamber to do work, e.g., drive blades of a gas turbine. As with any combustor system, control of the combustion process to reduce and control emissions and maximizing an operating space of the combustor system is advantageous.
In combustor systems with multiple can combustors, variation of can combustor operating conditions is a significant contributor to total emissions produced and reduced operating space resulting in loss of operability. In this regard, the combination of combustion chamber pressure (PCC) variation, combustion fluid (e.g., fuel) supply variation, and end cover effective area variation can drive can-to-can operation changes, and thus overall fuel-to-air (F/A) ratio and emissions variation. During planning of a combustor system, the fuel delivery system (manifold and flex hoses) that feed each can combustor are designed to minimize flow variation, caused by combustion fluid supply pressure variations, can-to-can. In addition, end cover and fuel nozzle arrangements are carefully arranged to minimize their effective area variation during manufacture, and over time. In operation, emissions variation is driven from, for example, the air flow in the form of nozzle throat area, air side leakages, and the impact of the back pressure applied from the combustion chamber in each can combustor. In the case of the latter contributor, higher or lower combustion chamber pressure impacts the pressure differential (dP) across the fixed area end cover, which results in can-to-can combustion fluid flow variation.